Axial flow compressor



Oct. 5, 1948.` K. BAUMANN y 2,450,745

um. now commassonA Filed April 6, 1944 Y 'lll/AU, I

Patented Gees', 1948 w 'Y 2,450,745.v UNITED PATENT QPF- ICEV 2,450,745AXIAL FLOW COMPRESSOR.

KarLBaumannLMera Knutsiford, England,l assignorto Metropolitan-VickersElectrical Company Limited, London, England, a company of Great BritainApplication Api-u s, 1944, serum. szasoz In Great Britain November l2,1942.

semen 1, Public Lawson, August s, 194e lPatent expires November 12, 1982s claims. (ci. eso-nir compressors, more particularly but notexclusively.

for use for propulsion suchas of aircraft.

In axial ow compressors of the uni-rotational type, that is to sayhaving moving and stationary blade rows, the rotational speed(revolutions per minute) which is permissible for a given mass flow islimited by the compressibility effects obtained. especially in theinitial compressor stages. Moreover, the diiiiculties arising fromcompressibillty effects decrease towards the high pressure end by reasonof the increased velocity of sound resulting from the increase ofthe-'temperature ,of the air at the high pressure end of the corn-ypressor. v y According to the present invention which enables therotational speed (revolutions per min` ute) of the compressor to beincreased for a given rate of flow of air or gas mass. and consequentlythe weight to be reduced not only of the compressor but also of theturbine or other prime mover driving it, the blade rows in the early orinlet stages of the compressor, which in a normal compressor would bestationary ones, are made to rotate in the same direction as that ofthe' rotor but at a rotational speed less than that ofthe carried froman auxiliary rotor housed within the normally stationary outer casing,the latter being suitably modified as to its shape, and thisauxilperature, the velocity of sound is reduced. Howpower is relativelysmall gears can be kept within reasonable limits. An importantsubsidiary feature of the invention isbased upon the consideration thatwhen the compressor forms part of an internal combustion plant forpropulsion of aircraft thecompressibility effects are particularlydifficult to deal with at high altitudes whereI owing to the low airtemtudes the thrust may be increased for a given rotational speed by theprovision of means whereby certain of the initial blade rows con-vcerned in the present invention as above set forth may temporarily beheld stationary. Thus, if the rotational speed -(revolutions per minute)of the plant is-limited by factors other than compressibility effectsunder these' low altitude conditions the speed reduction geararrangement maybe such that these initial stages are only permitted torotate at high altitudes where otherwise reasonable efficiency at fullspeed revolutions per minute could not be reached as a result ofcompressibility effects. Y

In carrying out vthis subsidiary feature "of the invention, thearrangement may be generally similar to that set forth above in somedetail,

with theexception that on the one hand vthe iary rotor is connectedthrough any convenient form of speed reduction gearing with the fullspeed main rotor of the compressor or with a part rotating therewith.-.In a convenient arrangement, the aforesaid auxiliary rotor ismechaniconnected at the outer periphery, with an outer cally and rigidlyconnected, preferably4 through an added row of blades precedingtheilrstrotating row attached to the main rotor, to an inner ring journalledonthe main rotor shaft; this ring carries a planetary shaft or axle, orpreferably several thereof distributed clrcularly around the axis of thecompressor, for one or.respective planet wheels as the case may be,peripherally engaging at a lesser radius a toothed wheel attached to themain rotor shaft, whilst at a greater radius 'thev planet wheel(s)engage(s) with an internally toothed stationary ring, the outerperiphery of which may conveniently form part of the inner wall of theair or gas passage at'the inlet end of the compressor. With thisarrangement, although power is transmitted through the planet gearingfrom the low speed rotor (auxiliary rotor) to the main rotor. the amountof'this auxiliary rotor is provided with braking means, such as aband-brake around its periphery, whilst on the other hand the-yinternally toothed ring engaged bythe outer diameters of the planetwheels is no longer fixed but mounted for' free rotation on the mainrotor shaft. Moreover, this internally toothed ring can'iesone or morerows of blading which will be the initial blade rowor rows for thecompressor, said row(s') being solidly ring with which is associatedfurther, and independently operable, braking means, such as aband-brake.- With this arrangement in the case where the compressorisemployed in conjunction with internal combustion plantfor propulsion ofan aircraft, for take-off and low altitude iiying performance thefirst-mentioned brake is applied. to the auxiliary rotor whereby theinitial lrow or rows of compressor blading is/are caused to rotate at alow speed in theopposite direction to that of the blading carried by themain rotor, the

second-mentioned brake being, ofcourse, released; for flying athighaltitudes the brake application is reversed, whereupon the initial rowor rows of blading become stationary as does lthe internally toothedring connected thereto, while the aux-- iliary rotor with its blade rowor rows rotates lin the same direction as 'that of the main rotor and atspeedwhich is less than that of the main rotor In order that the.invention may be fully iin-f derstoodreference will now be made to theace0 companylng diagrammatic drawing, the twofigv and the dimensions o fthe views of the upper half of alternative forms of axial now compressorconstructed and arranged in accordance with the invention and which aresuch as may be used, with advantage, in conjunctionwith internalcombustion plant for effecting propulsion of aircraft, although alsoapplicable for other purposes, like parts in the two igures, whenreferred to in the description, be-

r, of progressively lower mean diameter as is customary. Surrounding themain rotor is a stationary casing S carrying rows of high pressureblades s for co-operating with the corresponding main rotor blades r.This casing S extends axially beyond the main rotor cylinder R at theinlet end as shown S and is attached by circularly distributed webs, oneof which is indicated at y, to an inner disc SD supporting a bearing Bfor the main,rotor shaft RS. `The casing S will also provide amountingfor a bearing for the main rotor at the outlet or high pressure end ofthe compressor. I

Within the stationary casing S at the inlet end of the compressor andjust inrear of the -webs g which act as guides for the intake, there isdisposed a cylinder A, mounted for rotation concentrically with the mainrotor, and carrying rows of blades a for co-operating with the initialrows of main rotor blades ro. In this case, the cylinder A is attachedby a further row of blades ao, to an inner ring AR mounted on bearingsBA carried by the main rotor shaft RS. The inner ring AR carries aplurality of axles, one of which is indicated at PS, extending parallelwith the axis of the main rotor and circularly distributed therearound.each axle PS carrying a planet wheel P. 'Ihese planet wheels engageperipherally at a lesser radius with a toothed wheel RW fast to the mainrotor shaft RS and at a greater radius with an internally toothed ringSW which, in this embodiment of the invention, is represented as beingfast with the part SD of the stationary casing. Conveniently a labyrinthgland G is interposed between the auxiliary rotor cylinder A and theinterior of casing So in order that substantially the whole of the airor -gas intake shall be constrained to pass between the co-operating.main rotor initial blades ro, and the auxiliary rotor initial bladesro, and the auxiliary rotor blades ao, a.

With this arrangement, when the rotor shaft RS is rotating. therebytorotate the blades ro and r carriedfthereby in a given direction, theauxiliary rotor together with the blades at and a carried thereby willbe constrained to rotate in the same' direction and at a rotationalspeed which isless than that of the main rotor shaft, air or gas draw'ninto the compressor being acted upon by the relatively rotatinginitial,` main rotor blades ro on the one hand and the auxiliary rotorblades ao and a on the other hand. and being further compressed by theaction of the higher pressure co-operating main rotor blades r and mainstator blades a before being finally discharged from the compressor.

The rotation auxiliary rotor may be threaded over the main rotor inaccordance with the application of Joseph Stanley` Hall, Serial No.

518,181, led January 13, 1944.

.this case five, of higher pressure rows of blades The form ofcompressor illustrated in Fig. 2 is generally similar to that of Fig. 1in that it involves the provision, at the -inlet end of the compressor,of an auxiliary rotor comprising rotor cylinder A carrying blades ao,and a for mutual reaction with an initial row of blades ro carried bythe mainA rotor cylinder R, and whereof the blades an connect saidauxiliary rotor cylinder R. to an internal ring AR, which is journalledupon the main rotor shaft RS and carries the axles PS forcircularly-distributed planet wheels P engageable at a lesser radiuswith a toothed wheel RW fast with the rotor shaft RS and at a greaterradius with a toothed fring SW. However, in this form of the inventionthe outer toothed ring SW is not fast to the -stator casing SD as in theform of Fig. 1, but is mounted through arbearing BA1 on the rotor shaftRS and is attached by blades a; to an outer ring A1. Moreover, aband-brake A' is provided forengaging the outer periphery of theauxiliary rotor cylinder A and a band-brake A'i is provided for engagingwith the outer periphery of the ring Ai which as described, is attachedthrough blades a1 to the freely rotatable internally toothed ring SW.

lWith this arrangement, when the band-brake A' is operated accordinglyto restrain the auxiliary rotor against rotation notwithstandingrotation of the main rotor, and with the bandbrake A'i inoperative, theblades ai will be rotated'in opposite direction to that of the mainyrotor blades ro, withwhich they co-operate but at a rotational speedless than that of said blades ro; in the case of a compressor embodiedin internal combustion plant for the propulsion of an aircraft, thiswill be the condition established at take-olf and low altitude ilying.Conversely, with band-brake A' inoperative and the band-brake A'ioperated to restrain rotation of the bladed ring Ai, the initial bladesai will be stationarywhilst the auxiliary rotor blades au 'and a will berotated in the same direction as that in which rotate the main rotorblades ro, r but at a rotational speed which is less than that of saidmain rotor blades.

I claim:

1,A multi-stage axial-now compressor comprising a stationary casingcarrying a row of blades and having an inlet at on end for the admissionof fluid, a main rotor oused within the casing and carrying a, row ofblades for cooperating with the stationary blades to increase thepressure of fluid admitted at the inlet end of the casing, an auxiliaryrotor housed within the casing at the inlet thereof at which fluid isadmitted and carrying a, row of blades positioned in advance of said rowof blades on the main rotor, and diiferential mechanism comprising twosun wheels and a planet wheel intermeshing with said sun wheels whereofone sun wheel is attached to, for rotation with, the main rotor, whilethe planet wheel is rotatably mounted on the auxiliary rotor, and meansfor restraining the othersun wheel against rotation.

2. A multi-stage axial-flow compressor comprising a stationary casingcarrying a row of blades and having an inlet at one end for theadmission of uid, a driving shaft rotatably mounted in said casing, amain rotor attached to said shaft and housed within said casing and 5carrying a row of blades for co-operating with the stationary blades toincrease the pressure of fluid admitted at the inlet end of the casing,an auxiliary rotor mounted on said driving shaft at the fluid-admissionend of the casing and carrying a row of blades positioned in advance ofsaid row of blades on the main rotor, a gear wheel coaxially mounted on,and fast with, said driving shaft, an internally-toothed gear wheelcoaxially mounted on said driving shaft, a planet Wheel meshing withsaid gear wheels and rotatably carried by said auxiliary rotor, andmeans for restraining said internally-toothed wheel against rotation.

3. A multi-stage axial-flow compressor comprising a stationary casingcarrying a row of blades and having an inlet at one end for theadmission of uid, a driving shaft rotatably mounted in said casing, amain rotor driven by said shaft within said casing and carrying a row ofblades for co-operating with the stationary blades to increase thepressure of fluid admitted at the inlet end of the casing, an auxiliaryrotor mounted on said driving shaft at the fluid-admission end of thecasing and carrying a row of blades positioned in advance of said row ofblades on the main rotor, a gear wheel coaxially mounted on, and fastwith, said driving shaft, an internally-toothed gear wheel coaxial withsaid driving shaft and fast with the casing, and a planet wheel meshingwith said gear wheels and carried on said auxiliary rotor.

-4. A multi-stage axial-now compressor as claimed in claim 3, whereinsaid internallytoothed gear wheel forms an inner wall surrounded by thecasing to provide an annular passage for admission of fluid.

5. A multi-stage axial-now compressor comprising a stationary casingcarrying a row of blades, a driving shaft rotatably mounted in said mcasing. a main rotor attached to said shaft within said casing andcarrying a row of blades for co-operating with the stationary blades toincrease the pressure of iiuid admitted at one end ofl the casing, anauxiliary rotor mounted on said driving shaft at the fluid-admission endof the casing and carrying a row of blades for coperating with the rowof blades on the main rotor, an externally-toothed gear wheel coaxiallymounted on said driving shaft, an internallytoothed gear wheel rotatablecoaxially with respect to said driving shaft, a planet wheel meshingwith said gear wheels and carried on said auxiliary rotor, a releasableband-brake acting on the outer periphery of the internally-toothed gearwheel and a releasable band-brake acting upon the outer periphery of theauxiliary rotor.

6. A multi-stage axial-flow compressor comprising a stationary casingcarrying a row of blades, a driving shaft rotatably mounted in saidcasing, a main rotor rotated by said shaft within said casing andcarrying a row of blades for cooperating with the stationary blades toincrease the pressure of fluid admitted at one end of the casing andalso carrying an additional row of blades at the fluid-admission end ofsaid main rotor. a ring journalled on the shaft within the casing at theend thereof at which fluid is admitted, an outer ring surrounding saidinnerv ring and attached thereto by a row of blades adapted toco-operate with the said additional row of blades on the main rotor, agear wheel coaxially mounted 0n, and fast with, said driving shaft, aninternally-toothed gear `wheel ccaxial with said driving shaft, a planetwheel meshing with said gear wheels and journalled on a shaft carried bysaid inner ring, and means for restraining said internally-toothed wheelagainst rotation.

7. A multi-stage axial-flow compressor com prising a tubular casinghaving attached thereto a plurality of axially-spaced rows of blades, adriving shaft rotationally mounted in said casl0 ing and having attachedthereto a main rotor carrying a plurality of axially-spaced rows ofblades for co-operating with the stationary blades to increase thepressure of uid admitted at one end of the casing. together with anauxiliary rotor enclosed within the casing at the end thereof at whichuid is admitted, said auxiliary rotor comprising an inner ringjournalied on the shaft, an outer ring and a plurality of axially-spacedrows voi? blades carried by said outer ring for co- 0 operating withrows of blades on the main rotor and of which one row is attached alsoto the inner ring, a. plurality of gear wheels journalled at circularlydistributed locations on the inner ring. a gear wheel fast with thedriving shaft and meshing at a lesser radius with the circularly 8. Amulti-stage axial-now compressor comprising a casing having attachedthereto a plurality of axially-spaced rows of blades, a driving shaftrotationally mounted in said casing, a main rotor fast with said drivingshaft and carrying a plurality of axially-spaced rows of blades forco-operating with the stationary blades to increase the pressure of uidadmitted at one end of the casing, an auxiliary rotor rotationallymounted within said casing on said driving shaft and carrying a row ofblades for co-operating with the end row of main rotor blades at theuidadmission end, a second auxiliary rotor mounted within said casing atthe fluid-admission end and journalled on said driving shaftindependently of the mst-mentioned auxiliary rotor, and carrying a rowof blades. a differential gear mechanism connecting said driving shaftwith said second auxiliary rotor and the differential eleond auxiliaryrotor.

ment of which is connected to the first-mentioned auxiliary rotor, aband-brake peripheraiiy engageable with said first auxiliary rotor and a-band-brake peripherally engageable with said sec- KARL BAUMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Dah 832,124 Farmer Oct. 2, 1906901,228 Collier Oct. 13, 1908 911,653 Faywischewitsch Feb. 9, 1909y921,118 Kasley May 11, 1909 994,201 Robinson June 6, 1911 1,316,139Cake Sept. 16, 1919 2,224,519 McIntyre T Dec. 10, 1940 2,284,587 MullerMay 26, 1942 2,321,276 1 DeBolt June 8, 1943 '2,383,385 Heintze Aug. 21,1945

